JPH08327367A - Vibration sensor - Google Patents

Abstract

PURPOSE: To enhance sensitivity of a sensor and to improve the productivity and reliability by a constitution wherein vibration direction of a turning fork arm is limited in the X axis direction by adjusting a weight of an electrode for correcting a balance. CONSTITUTION: When a sensor is stopping having no external stress, voltage can not be generated in detection electrodes 3. However, when vibration direction of an arm is shifted from X axis of the sensor by an unbalanced condition due to lowering of etching process accuracy and an unbalanced condition of the electrode, the electrodes 3 output a detection voltage by receiving stress due to the shift between vibration direction of the arm and X axis of the sensor. It is eliminated by aligning the vibration direction of the arm to the X axis of the sensor because it is caused by the shift of the vibration direction and the X axis, then an electrode 4 for correction of balance is provided on the side face of a tip portion of the arm so that the balance is corrected. The correction is carried out maintaining the sensor in a quiescent state and vapor- depositing a metallic material on one of the electrodes 4 while monitoring the output of the sensor so as to set the output of the sensor to zero.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for offsetting an output signal of a vibrating sensor using a tuning fork type quartz oscillator by bending vibration.

[0002]

2. Description of the Related Art Generally, in a gyro using a bending oscillator and applying Coriolis, the detection sensitivity can be improved by adjusting the excitation side frequency and the detection side frequency to a twin resonance type. However, in the related art, when the twin resonance type is used, the vibration on the excitation side causes “vibration leakage” on the detection side to cause deterioration of sensitivity, so that the non-resonance type is adopted.

[0006]

Generally, when it is detected that the stress acting in the direction perpendicular to the Z'plane acts on the detection electrode 3 provided on the Z'plane of the tuning fork type vibrator, the tuning fork is normally operated. If only the X-axis is vibrating, no output is generated at the detection electrode 3 on the Z ′ plane. However, if there is an imbalance in the arm of the tuning fork and the vibration of the arm is mixed with the stress component not only in the X-axis direction but also in the Z'-axis direction, the stress in the Z'-axis direction is not applied from the outside. However, there was a problem that it was output as a detection signal.

[0007]

In order to solve the problem, a balance correction electrode 4 (no electric action, only weight) is provided on the top of the arm of the tuning fork of the crystal vibrating piece, and the weight is attached. The problem was solved by adjusting the direction of the vibration so that the vibration direction of the arm of the tuning fork of the crystal vibrating piece is correct only in the X-axis direction in the absence of external stress.

[0008]

FIG. 1 shows an embodiment of the electrode arrangement according to the present invention. A crystal piece called + 5 ° X-cut is cut in the Y-axis direction and processed into a U-shaped tuning-fork vibrator 1, and the Z ′ surface (4) of each arm near the base of the arm is processed.
A pair of electrodes having different polarities are arranged as the detection electrodes 3 on the surface. The drive electrodes 2 are arranged on the X-plane and the Z-plane of each arm near the tip of the detection electrode 3 of the arm. The location of the balance correction electrode 4 is provided on the side surface of the tip of each arm.

FIG. 2 shows an embodiment of a connection diagram of the drive electrode 2. The vibration direction vibrates in the direction in which the arm of the tuning fork opens and closes (X-axis direction). FIG. 3 shows an embodiment of a connection diagram of the detection electrode 3. As shown in FIG. 1, a pair of electrodes having different polarities are arranged on the Z ′ plane of each arm. One Z ′ plane of each arm will be described. In general, electrodes that are long in the Y′-axis direction and short in the X-axis direction are arranged adjacent to each other in the X-axis direction on the Z ′ surface to form a pair.

As shown in FIG. 3, since the same electrodes are arranged at the positions facing each other with the crystal piece interposed therebetween, contradictory voltages are generated between the electrodes facing each other in the pair. Since a voltage that is opposite to that of the electrode on the front side is generated between the electrode and the electrode, if counterclockwise rotation is applied as shown in FIG. 3, the quartz piece bends in the Z'direction due to the stress acting in the Z'axis direction. It will be. The displacement in the Y′-axis direction is that when one extends in the Y′-axis direction across the crystal piece, the other one contracts, so X
The electric fields generated in the axial direction have opposite directions on the surface facing the front surface of the crystal element.

As shown in FIG. 3, by connecting the pairs of the detection electrodes 3 in parallel with each other with the same polarity, the peak value proportional to the stress received by the arm at a frequency equal to the above-mentioned driving frequency. Output is obtained. FIG. 4 shows the detection circuit. The drive electrode 4 is connected to an oscillation circuit to oscillate. The output of the detection electrode 3 is amplified by an amplifier to detect the output.

A method for adjusting the arm balance will be described. When the sensor is stationary and is not subjected to external stress,
Essentially, no potential should be generated in the detection electrode 3. However, when the vibration direction of the arm deviates from the X axis of the sensor due to an imbalance due to the accuracy of outer shape processing such as etching or the imbalance of the electrodes, the detection electrode 3 deviates from the vibration direction of the arm and the X axis of the sensor. The detection voltage 3 is output as if the stress was received.

The above-mentioned phenomenon is caused by the fact that the vibration direction of the arm of the vibrator is deviated from the X axis of the sensor. Therefore, it can be resolved by aligning the vibration direction of the arm with the X axis of the sensor. 4 for balance correction on the side of
Is provided to correct the balance. The balance correction method is performed by depositing a metal on the balance correction electrode 4.
The sensor is held stationary, and metal is vapor-deposited on one of the electrodes for balance correction while monitoring the output of the sensor.

While the sensor is kept stationary, the deposited metal is blown to the balance correction electrode on either side while monitoring the output of the sensor. If the output of the sensor seems to increase, the vapor deposition is immediately stopped and the vapor deposition metal is blown to the balance correction electrode on the opposite side so that the output of the sensor becomes zero.

Note that the correction is not always performed only on the Z'plane. The X plane can also be used. Further, in this embodiment,
Although the detection electrode is arranged near the base of the tuning fork and the excitation electrode 2 is provided on the upper side thereof, the arrangement is not limited to this. The excitation electrode 2 and the detection electrode 3 may be arranged in reverse. further,
In the embodiment, an example of the vibration type sensor using the tuning fork type crystal unit of the bending vibration mode of + 5 ° X cut is given.
It is also effective for a vibration type sensor using a tuning fork type crystal resonator of bending vibration mode of up to + 6 ° X cut.

[0016]

According to the present invention, the output of the vibration type sensor using the tuning fork type crystal unit of + 5 ° X cut at rest can be offset to zero in the sensor itself, and the bi-resonance type sensor can be manufactured. As a result, a sensor with high sensitivity was obtained, sensor compatibility was facilitated, and not only the productivity and reliability of the sensor were improved, but also cost reduction was realized.

[Brief description of drawings]

FIG. 1 is a front view of a vibration sensor showing an embodiment of the present invention,
It is a side view and a top view.

FIG. 2 is a cross-sectional view and a connection diagram of drive electrodes of a vibration sensor showing an embodiment of the present invention.

FIG. 3 is a cross-sectional view and a connection diagram of a detection electrode of a vibration sensor showing an embodiment of the present invention.

FIG. 4 is a test circuit including a driving portion and a detecting portion according to an embodiment of the present invention.

[Explanation of symbols]

 1 tuning fork type vibrator 2 excitation electrode 3 detection electrode 4 balance correction electrode

Claims (1)

[Claims] 1. A vibrating sensor having a pair of electrodes of different polarities on a tuning fork arm on the Z'-plane of a bending vibration mode tuning fork type crystal resonator, wherein a balance correction electrode is provided at the tip of the arm. Vibration sensor characterized by.